Three-dimensional (3D) television has been a technology trend in recent years that is targeted to bring viewers sensational viewing experience. Multi-view video is a technique to capture and render 3D video. The multi-view video is typically created by capturing a scene using multiple cameras simultaneously, where the multiple cameras are properly located so that each camera captures the scene from one viewpoint. The multi-view video with a large number of video sequences associated with the views represents a massive amount data. Accordingly, the multi-view video will require a large storage space to store and/or a high bandwidth to transmit.
Therefore, multi-view video coding techniques have been developed in the field to reduce the required storage space and the transmission bandwidth. In three-dimensional and multi-view coding systems, the texture data as well as depth data are coded.
Currently, extensions of HEVC (High Efficiency Video Coding) are being developed, including screen content coding (SCC) and 3D extensions. The screen content coding targets at coding screen captured content, with non-4:2:0 color formats, such as 4:2:2 and 4:4:4, and video data with higher bit-depths such as 12, 14 and 16 bit-per-sample while the 3D extension targets at the coding of multi-view video with depth data.
One of the mostly likely applications utilizing SCC is screen sharing, over wired-connection or wireless. For video containing screen contents, coding tools have been developed by taking into consideration of the specific characteristics of screen-content and have been demonstrated to achieve significant gains in coding efficiency. Among them, the palette coding (a.k.a. major color based coding) techniques represent block of pixels using indices to the palette (major colors), and encode the palette and the indices by exploiting spatial redundancy.
In palette coding, a block of samples are represented by indices pointing to a table of representative colors (palette). The values of colors in palette are transmitted, together with the coded index map representing the block. An Intra coding technique using single color mode is disclosed in JCTVC-Q0093 (Chen et al., Single color intra mode for screen content coding, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 17th Meeting: Valencia, ES, 27 Mar.-4 Apr. 2014, Document: JCTVC-Q0093). In the single color mode, a block of pixels are represented by a single color, where the single color is derived from spatial and temporal candidate colors so that there is no need to transmit the color value.
The single color mode disclosed in JCTVC-Q0093 has demonstrated advantages in both improved performance (i.e., reduced bitrate) and reduced decoder complexity. It is desirable to develop techniques to further improve the coding efficiency of single color mode.